A young man returned from a backpacking trip in Mexico suffering from a high fever, pain in the abdomen, and watery diarrhea. The emergency room doctor noted a faint rash on the patient's abdomen andchest. A blood specimen was collected and plated onMacConkey agar, incubated at 37°C in ambient air. Lactose-negative colonies grew on the plates. The cultured organism was a Gram-negative rod that did not produce Shiga or Shiga-like toxins. The most likely etiologicalagent for this man's disease is:
A. Vibrio parahaemolyticus
B. Salmonella typhi
C. Shigella dysenteriae
D. Enterohemorrhagic Escherichia coli
Answer: B. Salmonella typhi
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Flight requires greater efficiency of oxygen delivery. Therefore, birds have a unique respiratory system that allows them to filter oxygen. During the initial inhalation, the air passes through the trachea and into the . During the second inhalation, the oxygen-depleted gas moves to the , and is then exhaled.
A. posterior air sacs; anterior air sacs B. lamellae of the gills; anterior air sacs C. anterior air sacs; posterior air sacs D. lamellae of the gills; bronchioles E. bronchioles; capillaries
The preassembled carbohydrate tree is added on_____ residue
Fill in the blank(s) with the appropriate word(s).
The sex ratio in a population is usually fixed and does not vary among age classes
Indicate whether the statement is true or false
Proper cross-matching of blood type is essential for safe blood transfusion
What is the general rule for safe blood transfusion, and what are the consequences if a patient receives the incorrect blood type by accident? If a patient's blood type is unknown, what is the safest course of action?